Art of trimming sheet metal pressings



Sept. 1% 1935. R. E. SMITH M4596 ART OF TBIMMTNG SHEET METAL PRESSINGS Filed June 2, 1934 4 Sheets-Sheet 1 O o A 15 O Z4 x 14 V M "Xl 43 FGJ.' 3

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|!I IIIIIIIIIIIIIIIIIIIlllillllmmllllllwllllll illl Patented Sept. 17, 1935 4' UNITED STATES PATENT OFFICE ART OF TRIMMING SHEET METAL PRESSINGS Richard Ernest Smith, Birmingham, England 19 Claims.

This invention relates to improvements in the art of trimming sheet metal pressings, and is intended primarily for application to the trimming of large sheet metal pressings.

f It is well understood that in making large sheet metal pressings, it is essential to leave a certain waste margin at the edge which subsequently has to be trimmed away, and it is to the trimming away of this edge to which the present invention relates.

At present it is the usual practice to trim in the press tools, or alternatively to trim in any rotary type of shears, the pressing usually being held in position by a second operator. This process is comparatively slow and the accuracy with which it is done depends almost entirely upon the skill of the operator. Inaccuracy in trimming is relatively common and one of the difficulties with which the operator has to contend is that after leaving the dies of the press, such pressings commonly move or distort somewhat out of shape.

The object of the present invention is to provide a means to ensure greater accuracy in trimming and to perform the operation with greater expedition.

Referring to the drawings:-

Figure 1 is a plan View of one form of jig and trimming tool constructed in accordance with one part of the invention and adapted to trim the edge of this pressing in accordance with a further part of this invention.

Figure 2 is a part sectional side elevation showing the trimming tool and a portion of the jig depicted in Figure 1.

Figure 3 is a section on the line 3-3 of Figure l.

Figures 4 and 5 are sectional views taken on the lines 4 4 and 5-5 respectively of Figure 3.

Figure 6 is a sectional View on the line 6-6 of Figure '7 showing a further form of trimming tool constructed in accordance with this invention.

Figure 'I is a part sectional plan view of the tool shown in Figure 6.

In the construction illustrated in Figures 1 to 5, the tool comprises a body I0 formed as a pair of cylindrical portions II joined integrally by a connecting web I2, and each of these cylindrical portions has rotatably mounted therein one of a pair of parallel spindles I3 and I4.

One end of each of the cylindrical portions is formed as one of a, pair of cylindrical extensions I5 and I6 to provide therebetween a space I'I for a purpose to be hereinafter described, and these extensions carry bearings I8 and I9 respectively, supporting the ends of the spindles.

The spindles I 3 and I4 project somewhat beyond the extensions, and their free ends have each detachably mounted thereon one of a pair 5 of shearing discs 2l) and 2I respectively.

These discs are respectively of a frusto-conical and cylindrical shape and are provided each with co-operating cutting edges 22 and 23 disposed in somewhat overlapping relationship.

For driving the spindles there is provided an electric motor 24 mounted on an arm formed integrally with the body of the tool, and this motor is adapted to drive a worm 26 which engages a worm wheel 2l arranged co-axially with the 15 inner end of the spindle I4.

In order to prevent any possibility of the shearing discs breaking under excessive load, the worm wheel 21 is arranged to transmit the torque through the medium of a friction clutch, and for this purpose it is formed on each side with one of a pair of conical clutch faces 28 which engage corresponding faces formed each on the end of a pair of clutch sleeves 29 and 30 arranged co- -axially with respect to each other and to the inner end of the spindle.

The inner of these clutch sleeves extends beyond the adjacent end of the spindle as well as beyond the outer sleeve, and this extension has mounted thereon an annular resilient bush 3l 30 formed from rubber and carries at its extremity a clutch adjusting nut 32.

Each side of the bush is engaged by one of a pair of annular metal discs 33 mounted on the said inner sleeve, and these discs are engaged respectively by the end of the outer sleeve and by the clutch adjusting nut 32.

Thus, on rotating the nut 32, the two sleeves can be caused to slide axially relative to each other and to engage resiliently the clutch faces 28 40 of the worm wheel, so that the transmitted torque is dependent solely on the pressure exerted by the resilient bush 3l, and can be limited to a value considerably below that necessary to strain or mutilate any part of the machine.

The drive is transmitted from the two sleeves to the spindles by forming the inner sleeve with a slot 34 which engages a key 35 provided on the spindle I4, while the outer sleeve 3Q is formed adjacent the worm Wheel 2l with a plurality of 50 peripheral teeth 36 which engage a toothed wheel 3l carried on the inner end of the spindle I3.

Conveniently, these teeth and the toothed wheel are so arranged that the same peripheral velocity is imparted to the cutting edges of the discs.

'I'he whole of the drive mechanism is enclosed by a detachable cover 38, and this may be lled with oil while a further detachable cover 39 is provided for enclosing the clutch adjusting mechanism.

In order to compensate for any relative Wear which may take place between the two shearing discs, the spindle I4 is capable of a limited sliding movement in an axial direction, and for this purpose the bearing I9 is arranged to screw into the extension I6 of the body while for controlling such movement the inner end of the spindle carries a pin 40 which extends beyond the clutch adjusting nut 32 and is provided at its free end with suitable locking nuts and washers which engage the adjacent end of the inner sleeve 29 so that the spindle can be slid axially relative to the latter.

The jig for holding the sheet metal pressing and for clamping it to its required nal shape comprises a body portion 4| shaped to engage the outer surface of the pressing and a movable wooden clamp portion 42 for engaging the inner surface of the pressing to hold it securely to its iinal shape, and these portions are so arranged that on assembly of the jig the edge to be trimmed projects somewhat beyond the two portions.

The body portion 4I is provided adjacent the edge of the pressing with a metal facing 43 which extends longitudinally of the edge and for the full length thereof, and this facing and the wooden clamp portion 42 are each provided with longitudinal faces 43a and 43h respectively ior engaging and supporting the edge portion oi the pressing.

Formed on the upper or exposed surface of the facing 43 is an undercut slot 44 of somewhat .L shape which extends for the full length of the facing, and at a constant distance from the longitudinal face 43a which engages the edge oi the pressing.

The base part of one of the undercut portions of the slot is formed as a toothed rack 45 which extends ior the full length of the slot.

The spindle I3 of the trimming tool is arranged to extend beyond the shearing disc 20 and carry adjacent thereto a wheel 46 provided with a plurality of peripheral teeth which are adapted to co-operate with the rack 45 to propel the trimming tool along the exposed edge of the presslgI'he wheel 48 is of shouldered form to provide a face 'H which engages the sides of the slot whereby the tool is positioned positively therein with respect to the clamping device and to the exposed edge of the pressing so that by virtue of the uniform distance of the slot from the face 43a., the tool will travel along the exposed edge of the pressing with the cutting means at a constant distance therefrom.

In order to provide additional means for guiding the tool, there are arranged on opposite sides of the wheel 4B one of a pair of guide discs 4i which engage the sides of the upper portion of the slot, and these guide discs are carried by one of a pair of arms 48 which depend from an open rame 49 which embraces the body l!! of the trimming tool.

To permit of the tool travelling in curves of varying radius, this frame is arranged to slide relatively to the body and transversely to the travel of the tool.

In order that the trimmed edge may be afterwards Welded, it is sometimes advisable that it should be curved outwardly of the plane of the adjacent portion of the pressing and for this purpose, the cutting edge of the shearing disc 2! is chamfered as at 5E) and arranged to co-operate with a correspondingly shaped edge 5! formed on the adjacent facing 43 so that the trimmed edge after shearing is formed immediately with a ila-nge 52 of curved form, which can be welded subsequently without the necessity for the performance of further work thereon.

In employing apparatus of the kind described above for trimming sheet metal pressings, the pressing is inserted in the jig in the usual manner with the edge to be trimmed exposed, whereupon the trimming tool is positioned relatively to this edge with the wheel 46 disposed within the slot 44 which has its ends made open for this purpose, and the motor is operated to drive the shearing discs and to rotate the toothed wheel 46 so that the exposed edge is sheared and the tool travelled along the edge simultaneously and in an automatic and continuous manner.

By arranging for the toothed wheel to be driven from the same source of power as the shearing discs, the advancement of the tool is made proportionate to the cutting speed of the cutting edges of the shearing discs.

In some cases, it may be necessary to carry out a preliminary cropping of the edge of the pressing as otherwise this may foul the trimming tool, but normally this is not required since the untrimmed edge extends into the space Il between the spindles as shown at 53.

A trimming tool of this kind is particularly advantageous for trimming large pressings having edges of varying radius since it can be advanced along such curved edges at a uniform speed.

If desired, for steadying the tool it may be provided with a handle 54.

Figures 6 and 7 show a modied form of portable trimming tool which is arranged to provide a more extensive space for the reception of the untrimmed edge and to avoid the necessity for any preliminary cropping of the metal, and this tool comprises a main body 55 having a pair of arms 56 and 51 which project therefrom in spaced parallel relationship to provide therebetween an extensive gap 58 for the reception of the uncropped edge.

The arm 56 is somewhat longer than the arm 5l, and each of these carry respectively at their extremities spindles 59 and 60 which extend towards each other and are provided at their adjacent ends with shearing discs 6| and 62 respectively disposed with their edges in co-operating and overlapping relationship as in the previous construction.

For actuating the spindles, there is provided in the body 55 of the trimming tool, an operating shaft 63 which drives the spindles through the medium of two trains of gearing 64 disposed one in each of the two arms.

Conveniently, the operating shaft is driven from an electric motor 64a through the medium of a worm 26 and wornr wheel 21 as in the construction described above.

Fcr holding the pressing, there is provided a jig of a form similar to the previous construction including a facing 43, and this facing is formed adjacent the edge of the metal with a flange B5, and the inner face of this flange is formed with a slot 12 extending for the full length of the facing and at a constant distance from the face 43a thereof, and this slot is formed with a rack 66 which is adapted to be engaged by the train wheel 61 mounted on the spindle 60 carried by a shorter arm, to advance the tool simultaneously with the shearing of the edge in a manner similar to the previous construction.

For guiding the tool, the shorter arm carries `a guide peg 63 extending outwardly therefrom and engaging a slot 69 formed in the adjacent surrace of the facing and extending for the full length thereof.

For curving the trimmed edge to enable it to be subsequently welded, the shearing disc 62 is of {ruste-conical form to provide an undercut cutting edge li).

What I claim then is:-

1. A method of trimming sheet metal pressings of hollow form which comprises placing the pressing in a clamping device having associated therewith means for guiding a trimming tool, manipulating the clamping device to clamp edge portions ci the pressing to their required nal hollow shape, supporting .said edge portions with the edge to be trimmed exposed, engaging the tool with the guide, and travelling it bodily along the guide and bodily along the edge of the pressing to trim the exposed edge.

2. A method of trimming sheet m'etal pressings of hollow form which comprises placing the pressing in a clamping device having associated therewith means for guiding a trimming tool, engaging the tool with the guide, travelling it bodily along the guide and bodily along the edge of the pressing to trim the exposed edge, and simultaneously bending the edge to form a readily removable welding flange.

3. Apparatus for trimming sheet metal press- 'igs, comprising a portable trimming tool, including in combination a body, a pair of spindies associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in cci-operating relationship, an electric motor mounted on said body and associated operably with said spindles, and clutch means adapted to transmit a given maximum torque between said motor and shearing members.

4. Apparatus for trimming sheet metal pressings of hollow form, comprising the combination of a clamping device, and a portable trimming tool, said clamping device including means adapted to clamp edge portions of the pressing to their required nal hollow shape and to support said portions with the edge to be trimmed exposed, a guide for guiding the tool during trimming, and a rack, the latter and the guide extending longitudinally of said clamping means, and said tool including a body, a pair of spindles associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in cooperating relationship, means for driving said spindles, positioning means adapted to engage the guide, a toothed wheel associated rotatably with the tool, said wheel being associated operably with said driving means, and said wheel being adapted to engage the rack to advance the tool longitudinally of said clamping means to trim the exposed edge of the pressing.

5. Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device, and a portable trimming tool, said clampj ing device including means for supporting edge portions of the pressing with the edge to be trimmed exposed, the clamping device having a guide slot extending longitudinally of said supporting means and in substantially parallel relationship with respect thereto, said guide slot having a recess extending longitudinally thereof, a plurality of teeth spaced longitudinally apart disposed in said recess, and said tool including a body, .a pair of spindles associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in co-operating relationship, means mounted on said body for mechanically driving said spindles, a wheel associated with one of said spindles, and adapted to enter the guide slot and to engage said teeth, said wheel having a shouldered portion adapted to engage a face of said recess and retain the wheel Within the slot, and a pair of guide portions mounted movably on said body, said guide portions being disposedin spaced relationship and adapted to engage said guide slot.

6. Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device, and a portable trimming tool, said clamping device including a facing adapted to support the pressing adjacent the edge thereof, said facing having an edge portion of curved form, and said tool including cutting means adapted to trim the edge of the pressing, means for advancing the tool to trim the edge of the pressing, a disc having a curved periphery adapted simultaneously with the advancement of the tool to engage the trimmed edge of the pressing with the said curved edge portion of the facing to form on said trimmed edge a welding flange, and means for guiding said tool during its advancement and for maintaining said disc adjacent said edge portion.

7. A method of trimming sheet metal pressings of hollow form which comprises placing the pressing in a clamping device having associated therewith means for guiding a trimming tool, manipulating the clamping device to clamp edge portions of the pressing to their required final hollow shape, supporting said portions with the edge to betrimmed exposed, engaging the tool with the guide, travelling it along to trim the exposed edge of the pressing, and simultaneously bending the edge to form a welding flange.

8. Apparatus for trimming sheet metal pressings of hollow form comprising the combination of a clamping device, a portable trimming tool, anda guide for guiding the tool during trimming, said clamping device including means for supporting the pressing with the edge to be trimmed exposed, and said tool including a body, a pair of spindles associated rotatably therewith, a shearing disc carried by each of said spindles, said shearing discs having cutting edges disposed in cooperating relationship, means mounted on said body for mechanically driving said spindles, positioning means adapted to engage removably the guide, said guide being adapted to co-operate with said positioning means and position the shearing discs positively with respect to the pressing, and means for advancing the tool along the guide to trim the exposed edge of the pressing.V

Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device. and a portable trimming tool, said clamping device including means for supporting edge portions of the pressing with the edge to be trimmed exposed, the clamping device having a guide slot extending longitudinally of said supporting means and in substantially parallel relationship with -respect thereto, a plurality of teeth spaced longitudinally apart disposed in said All spindles associated rotatably therewith, a shearing disc carried by each of -said spindles, said shearing discs having cutting edges disposed in oo-operating relationship, means mounted on said body for mechanically driving said spindles, a toothed wheel operably associated with said driving means, and adapted to enter the guide slot and to engage said teeth, and said wheel having a shouldered portion adapted to engage a face of said slot and position the shearing discs in relation to the exposed edge of the pressing.

l0. Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device, and a portable trimming tool, said clamping device including a facing adapted to support the pressing adjacent the edge thereof, said facing having an edge portion of curved form, and said tool including a body, a pair of spindles associated rotatably therewith, a shearing disc carried by each of said spindles, said shearing discs having cutting edges disposed in co-operating relationship, means for driving said spindles, means for advancing the tool to trim the edge of the pressing, means for guiding said tool and for maintaining one of said cutting discs adjacent said edge portion of the facing during the advaneement of said tool, and said latter cutting disc having a curved edge adapted during the advancement of the tool to engage the trimmed edge of the pressing with the said curved edge portion of the facing to form on said trimmed edge a welding flange.

11. In apparatus for trimming sheet metal pressings, a portable trimming tool, including in -combination a body, a pair of spindles associated rotatably therewith, a shearing disc carried by each of said spindles, said shearing discs having cutting edges disposed in co-operating relationship and adapted to engage opposite sides of the edge of the pressing, means mounted on said body for mechanically driving said spindles, means for advancing the tool to trim the edge of the pressing, and one of said shearing discs having a curved periphery of concave form in cross section adapted simultaneously with the trimming of the pressing to bend the trimmed edge thereof and form a welding flange.

l2. A method of trimming sheet metal pressings of hollow form, which comprises placing the pressing in a clamping device having associated therewith means for guiding a trimming tool, engaging edge portions of the pressing on opposite sides thereof, manipulating the clamping device to clamp said portions to their required final hollow shape, supporting said portions along substantially their whole length with the edge to be trimmed exposed, engaging the tool with the guide, and travelling it along to trim the exposed edge of the pressing.

13. A method of trimming sheet metal pressings of hollow form which comprises placing the pressing in a clamping device having associated therewith means for guiding a trimming tool, engaging edge portions of the pressing on opposite f sides thereof, manipulating the clamping device to clamp said portions to their required nal hollow shape, supporting said portions along substantially their whole length with the edge to be trimmed exposed, engaging the tool with the guide, travelling it along to trim the exposed edge of the pressing, while simultaneously bending the trimmed edge outwardly from the interior of the hollow pressing to form a welding flange.

14. Apparatus for trimming sheet metal pressings of hollow form, comprising the combination o-f a clamping device, a portable trimming tool and a guide adapted to guide the tool bodily along the edge of the pressing during trimming, said clamping device being adapted to clamp edge portions of the pressing to their required final hollow shape and to support said portions with the edge to be trimmed exposed, and said tool including cutting means adapted to trim the edge ci the pressing, positioning means adapted to engage the guide, and means for advancing the tool bodily along the guide and bodily along the edge of the pressing to trim the exposed edge.

l5. Apparatus for trimming sheet metal pressings of hollow form, comprising the combination oi a clamping device, a portable trimming tool and a guide adapted to guide the tool bodily along the edge of the pressing during trimming, said clamping device being adapted to clamp edge portions of the pressing to their required nal hollow shape and to support said portions with the edge to be trimmed exposed, and said tool including movable cutting means adapted to trim the edge of the pressing, means for mechanically driving said cutting means, positioning means adapted to co-operate with said guide and position said cutting means positively with respect to the edge of the pressing, and means adapted to advance automatically the tool bodily aiong the guide and bodily along the edge of the pressing to trim the exposed edge.

i6. Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device and a portable trimming tool, said clamping device including means for supporting edge portions of the pressing with the edge to be trimmed exposed, the clamping device having a guide slot extending longitudinally of said supporting means, said guide slot having a recess extending longitudinally thereof, and said tool including a body, a pair of spindles associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in co-operating relationship, means for driving said spindles, means adapted to co-operate with said guide slot and said recess and position said shearing members positivelyT with respect to the edge of the pressing, and means for automatically advancing the tool along the guide to trim the exposed edge of the pressing.

17. Apparatus for trimming sheet metal pressings comprising a portable trimming tool, including in combination a body, a pair of spindles associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in co-operating relationship, means mounted on said body for mechanically driving said spindles, positioning means adapted to engage a guide, means adapted to advance automatically the tool along the guide to trim the exposed edge of the pressing, a pair of guide portions mounted movably on said body, said guide portions being disposed in spaced relationship and adapted to engage said guide and position the tool in relation to the pressing.

18. Apparatus for trimming sheet metal pressings, comprising a portable trimming tool, including in combination a body, a pair of spindles associated rotatably therewith, a shearing member carried by each of said spindles, said shearing members having cutting edges disposed in co-operating relationship, an electric motor mounted on said body, a wheel associated operably with said motor for imparting torque therefrom to said spindles, a pair of clutch sleeves arranged concentrically with respect to one another and associated operably one with each of said spindles, each of said sleeves having at one end a clutch face engaging frictionally said wheel at opposite sides thereof, and resilient means connecting the opposite ends of said sleeves adapted. to apply pressure to opposite sides of said Wheel.

19. Apparatus for trimming sheet metal pressings, comprising the combination of a clamping device, and a portable trimming tool, said clamping device including a facing adapted to support the pressing adjacent the edge thereof, said facing having an edge portion of curved form, the clamping device having also a guide slot eX- tending longitudinally of said supporting means and in substantially parallel relationship with respect thereto, a plurality of teeth spaced longitudinally apart disposed in said guide slot, and said tool including a body, a pair of spindles associated rotatably therewith, a shearing disc carried by each of said spindles, said shearing discs having cutting edges disposed in co-operating relationship, means mounted on said body for mechanically driving said spindles, a toothed Wheel operably associated with said driving means, and adapted to enter the guide slot and to engage said teeth, said wheel having a shouldered portion adapted to engage a face of said recess and position the shearing discs in relation to the exposed edge of the pressing, and means adapted during the advancement of the tool to engage the trimmed edge of the pressing with the said curved edge of the facing to form on said curved edge a Welding flange.

RICHARD ERNEST SMITH. 

